'94 LT1 F-Body/ $EE tuning change for '95 transmission (PWM)

[Gojira94]

I created a thread on the TunerPro forum last fall but thought it might get more eyes here:

Posted last fall:




Need to know what I need to add or change for adding control of the PWM solenoid for a 95 4L60E in a 94 PCM. I already ran an extra pin from trans case connector ("U") to blue connector "C", pin 6.

I had the PCM re-flashed by a reputable tuner in the southeast US. They said it'd be re-flashed with "95 base code" to handle the 95 trans in a 94 car (didn't know it was a 95 PWM trans, was there when I bought it 900 miles after installation of it) I want to make sure what I should see if this is so is there. Mechanically, it's all correct, but I still have no TC lockup or 4th gear.



And an update from today (moved to a place where I can wrench almost every day!)

07-20-16:
I finally pulled the tune from the PCM after some troubleshooting connections to power the ALDL cable. I'm not sure what I'm looking for in TunerPro, but I sorted by parameter category to focus on transmission. I can't see anything that looks like PWM where I expected to see it under Torque Converter Lockup (TCC). I'm starting to doubt that the base tune I have is actually 1995 code. I cleared the code 84 and it came right back. I have a quick disconnect for the wire from PWM solenoid to case connector U on the trans. When I disconnected it I also got a code 83, which went away again after I reconnected the PWM/ Pin U wire.

Maybe find a known 95 auto BIN and look at it to tell? I don't know at this point. If that's the answer I could merge the BIN I have with one that's a known 95 to transfer the mail order tune parameters to a known 95 BIN. Tedious, but one way to do it, I guess.

.bin file and change log uploaded (I updated a couple of things that needed it while I was at it.

[steveo]

tunerpro has a bin compare function, perhaps compare your bin to a factory '95 cal? i maintain a large archive of bin files at http://fbodytech.com/bin-files-2/bin-files/

there's a guy here that has gone from a '94 trans to a '95 trans and knows all the tricks. i think it might be brian. he'll probably chime in soon, i don't know much bout autos...

i bet the 'mail order tune' is pretty minimal too, you could pull the calibration ID from that bin and maybe compare with the stock one and see what changes are made

[Gojira94]

tunerpro has a bin compare function, perhaps compare your bin to a factory '95 cal? i maintain a large archive of bin files at http://fbodytech.com/bin-files-2/bin-files/

there's a guy here that has gone from a '94 trans to a '95 trans and knows all the tricks. i think it might be brian. he'll probably chime in soon, i don't know much bout autos...

i bet the 'mail order tune' is pretty minimal too, you could pull the calibration ID from that bin and maybe compare with the stock one and see what changes are made

I did a compare against a common bin out there (95 A4 z28 3.23) and saw across the board differences in the TCC vs. xyz tables. Not sure what else makes the difference, don't really know what I'm looking at with auto trans parameters or where the differences are between 94 & 95 in regard to using PWM to do the TCC apply strategy.

This car has minimal mods- Moroso CAI, Pacesetter offroad headers, 3" X-pipe to 2.5" reduction off the back of the x to 2-chamber Flowtech Afterburners dumped at the axle. The mail order tune didn't even seem to adjust the O2 relocation stuff and missed a couple things in actually disabling EGR and AIR (just turned off codes). Tune was stated to have "adjusted the line pressure and shift firmness." I didn't get into the timing tables to see if anything was improved there.

[lionelhutz]

The info in Tunercat says the bin is from a 94.

10802

[jthompson122183]

the bin is indeed 94,calibration id 16202131. 10803 from fbodytech.com10809
the big difference is the addition of the tcc apply pressure(pwm) for 95
but whoever did the tune used the 95 changes in the bin.

in the 94 calibration these are 0 in the tables and some other parts of the bin. the tuner changed these to what the 95 has.
yours is 10804
factory is 10805

the only operating system difference between the 94 and 95 is at subroutine 4db2 on tside chip 10806

looking at ida here is the os subroutine10807



i've attached the factory 16202131 calibration

hope this helps you out

Jonathon

[lionelhutz]

Remember that Tunerpro and Tunercat both use definitions to map the bin. There are 2 tables for PWM control - PWM Apply Rate and PWM Release Rate. CATS or Tunerpro definitions can map these table areas and still be used for any year of bin. But, if the bin doesn't have the 95 PWM code Jonathan pointed out then the mapped areas are not legitimate tables and changing them does nothing useful. In 94 they are not really a table but rather just empty blank space on the chip.

That compare Jonathan posted shows the tuner attempted to turn a 94 bin into a 95 bin, which doesn't work as you now know.

[Vaild]

I need help and I don't know how to post but I have a 94 K1500 5 speed I am doing a v8 swap I have a 4.3 I am putting a 96 305 in my truck that Iswitch to tbi but I'm going to the junk yrd will an auto ecm work with my5 speed I heard it will just throw a check engine light

[Gojira94]

jthompson122183, lionelhutz

Great information, thanks for confirming. I had wondered why you couldn't just add the PWM programming into a 94 bin. It totally makes sense since the calibration ID determines whether or not the tables even exist for PWM. Like writing data into a region of the chip that the calibration never intends to read.

So... I think I'm done with doing anything else with this tuner in the mail order realm. I have reputable dyno tune outfits nearby if I go any further with this car. In the meantime I need to find a calibration for a 95 Formula that has the transmission performance button and 2.73 gears and simply do a few things I know how to do already in TunerPro. Maybe study the spark advance tables my tuner did and see if they are of any real benefit. If I'd known 5 years ago what I know now, I'd have done all this myself and saved 175.00 for the mail order and 75.00 for the '95 reflash.'

I just want the transmission problem gone so I can do the one other thing I want to do with this car- change gears to 3.42. I'm putting 4.10s in my M6 and planned to put the 3.42s in the car, using a ring spacer for the 2-series carrier. Which gives rise to the next question, which I can take to a different thread perhaps: I know how to change the speedo stuff, but what about the shift points? Is that all TPS vs. VSS vs. RPM? Do I need to account for the gear change elsewhere in the tune?

[Gojira94]

I pulled calibration ID EE_16210041 from Steve O's site (thanks, Steve). I made some edits to compensate for the O2 relocation with headers per TunerPro suggestion, desensitized the knock sensor a bit since I have a factory KM (probably unnecessary since I have headers but still have factory stamped steel rocerks at the moment), turned off and disabled AIR and EGR. I didn't do anything with timing at this point. I think this should be good enough to load into my PCM and see if the PWM stuff works like it should and the DTC 84 goes away once and for all. Modded bin and log attached. Thoughts/ opinions?

Thanks,

Rob B

[Gojira94]

I tried loading the modded 95 bin using C.A.T.S. I purchased about a year ago for my M6 car. I can read vehicle info, read and save old bin. I try to program the PCM and Establishing communications part is fine, fans kick on for 2-3 seconds as normal. When it then starts the 'erasing PCM' part, it fails after about 1 second with the message "Error: Invalid response from PCM"

So I thought maybe PCM says "I'm 94. No 95 programming for me." I changed the VIN year character from R to S and the "Current Model No." from 16202131 to the same as the one for the bin I'm trying to load, 16210041. That didn't change anything. Same error after repeated attempts with different combinations of KOEO, plug in cable, start winflash program , etc.

Will try EEHack next?

[Gojira94]

Using $EEHack on XP SP3 (unsupported, I know, but only laptop I have with a COM port). Stability test completes without any problems. Failed to upload new bin.

Applying VPP (EEPROM Programming) voltage
Failed to upload program to apply VPP HI voltage

(?)

This car is a stubborn little piglet. And I'm probably doing something incorrectly.

[Gojira94]

So from reading up on VPP here and there, it looks like a clue may be in battery voltage. I read that VPP can be 21V, 25V, 12.5V, perhaps others. The battery I was using had dropped to about 11.6V from all the KOEO fuel pump priming, so I grabbed the identical battery from my recently acquired 92 TBI truck (next project). It initially read 12.32V. After having some connection problems again getting sufficient power to the 12V input for the aldl cable (getting tired of fiddling with that), I was down to about 11.92V. So is my issue that the PCM doesn't see enough voltage to safely go into programming mode and fails the VPP check subroutine? My only other thought is to try another PCM. I have a spare about 10 miles away. I feel so close to finally solving this car's problem I can hardly stand it. Like 4th and goal, inches to go...

[steveo]

you'll definitely need a high enough voltage at the ECM to program.

1994 and 1995 program exactly the same, so that's not the issue.

you need to be really careful, this is probably a warning sign. continuing might mean bricking your ecm if you have unstable power.

what kind of aldl cable are you using that still needs 12v input? that might be a contributing factor? it's 2016, get a usb one already...

[Gojira94]

you'll definitely need a high enough voltage at the ECM to program.

1994 and 1995 program exactly the same, so that's not the issue.

you need to be really careful, this is probably a warning sign. continuing might mean bricking your ecm if you have unstable power.

what kind of aldl cable are you using that still needs 12v input? that might be a contributing factor? it's 2016, get a usb one already...

Thanks for the insight. I don't have an RS-232 to USB with an FTDI chip but I'm considering another ALDL cable. Before I ran out of time yesterday I hooked up a charger to supplement the battery voltage and connected a meter to the leads on the 12V lighter outlet to monitor voltage. I was getting between 12.25-12.35V before that. After, I was getting about 12.72. The courtesy lights and door dinger and radio display (even when off) were droping it to 12.55-12.60V. The fuel pump and fans cycling dropped it below 12.4V in a hurry. So I tried pulling the fan relays and fuses for radio and courtesy. Fuel pump alone was enough to drop it to 12.45 when it cycled. Next, I'm headed back out to disconnect the fuel pump relay so I have nothing but the ALDL 12V and PCM draw on the system to see where that lands voltage-wise. If that doesn't cut it, I guess I'll be building a bench to flash my PCM. Funny thing is I have zero issues with my M6 car and its battery isn't quite as strong as the one in this car that I borrowed from the truck Tempting to flash it in that car...

[Gojira94]

Update:

I tried flashing the PCM in my other F-Body (M6), same result with both Winflash and $EEHack. I had hoped that without a transmission to possibly feed any voltage to, that might help. I would have assumed trans circuits are not energized until engine start, but thought it was worth a shot anyway. Next, I tried my spare PCM from a 94 Z28. Same result, still with charger adding support to 12V system on the car. I did pull the fuel pump relay so it took priming that out of the load at KOEO. Then I started pulling every other fuse except PCM IGN, PCM BATT and CIGAR/ACCY. That brought me to 13.16V at KOEO with ALDL talking. It's like that 1996 movie Apollo 13...

So, with 13.16V read at the lighter socket, something is still lacking. As I'm writing this, I'm dope slapping myself for not doing one simple thing: Check the voltage across the fuse slots for PCM-IGN and PCM-BATT. I've read elsewhere that some believe there is "something in the dash wiring" on some of these cars that's an issue in these cases.

So at this point I'm heading off to research how to build my own bench for flashing the PCM out of the car. Hopefully I can use my RS-232 ALDL cable for some of the parts- likely just clips to the pins on the ALDL end, feed it with a jump box that has a lighter jack (have one). Same for the data link, and feed the PCM with a AC input/ DC output multi-voltage setting wall adapter that can feed the PCM from 12 to 13.5 volts, whatever it wants. Will need a couple PCM connectors, had 2-3 from a 94 Blazer or something from a local boneyard, not sure where they are. Just need the pinouts for the ALDL side, but that's well documented. Off I go... thanks for all the help. Gotta love the EFI community, great bunch. Any other thoughts/ advice welcome.

Thanks

[Gojira94]

This is what I put together a little while ago. I made it as simple as I could, using what I had and what I understood of the connections. I found the PCM connectors I had. One was red, the other blue. So I scraped off the key on the red one and am using it as my black connector. I used Gerry Massie's 2 connector OBDI/OBD2 benchtop diagram to guide me http://www.gmassie.net/13secss/pcm_harness.html and just left off the OBD2 data wire. I guess I could always add it later if I wanted to. I need a switch for the ignition wire to make it pretty (double pole, single throw?) and my 12V & ground source. I have a 12V wall adapter somewhere, need to check the mA rating on it. Not sure how many mA (or full Amps) I need. Here's what I have so far. I used spade connectors to connect to ground and serial data on my ALDL cable.

[Gojira94]

So I had to try it out. It connects in TunerPro, but not in $EEHack or Winflash. Winflash gives squat for logging, but I turned on verbose debug in $EEHack and got the following:

Loading Definition DEVICE=0xF4 MSG=0x0 Loading Definition DEVICE=0xF4 MSG=0x1
Loading Definition DEVICE=0xF4 MSG=0x2
Loading Definition DEVICE=0xF4 MSG=0x3
Loading Definition DEVICE=0xF4 MSG=0x4
Loading Definition DEVICE=0xF4 MSG=0x5
Loading Definition DEVICE=0xF4 MSG=0x6
Loading Definition DEVICE=0xE4 MSG=0x0
Loaded 1014 elements into 8 definitions.
VERSION re-checking, network went online!
VERSION offline status, skipping versioning
Using monotonic reference clock.
EEHack Version 4.60
Current OS : Windows XP
Built with THROTTLE_MS=2
Opened serial port COM1 Description Communications Port MFR (Standard port types)
START SILENCE ROUTINE
SERIAL: ECHO CORRUPT! (bad serial interface?)
SERIAL: ECHO CORRUPT! (bad serial interface?)
START SILENCE ROUTINE
SERIAL: ECHO CORRUPT! (bad serial interface?)
SERIAL: ECHO CORRUPT! (bad serial interface?)
START SILENCE ROUTINE
SERIAL: ECHO CORRUPT! (bad serial interface?)
[SERIAL WRITE]*F45608AE
[SERIAL DISCARD ECHO]
[SERIAL READ]*FA030000
SERIAL: ECHO CORRUPT! (bad serial interface?)
START SILENCE ROUTINE
Listening 2000ms for broadcast heartbeat...
Timeout waiting for heartbeat after: 2000ms
SHUTUP DEVICE f4
[SERIAL WRITE]*F45608AE
SHUTUP DEVICE f9
[SERIAL WRITE]*F95608A9
DATASTREAM: Send MODE8 keepalive*F95608A9
[SERIAL WRITE]*F45608AE
[SERIAL DISCARD ECHO]
[SERIAL READ]*B7030000
SERIAL: ECHO CORRUPT! (bad serial interface?)
[SERIAL WRITE]*F45608AE
[SERIAL DISCARD ECHO]
[SERIAL READ]*70040202
SERIAL: ECHO CORRUPT! (bad serial interface?)
START SILENCE ROUTINE
Listening 2000ms for broadcast heartbeat...
Timeout waiting for heartbeat after: 2000ms
SHUTUP DEVICE f4
[SERIAL WRITE]*F45608AE
SHUTUP DEVICE f9
[SERIAL WRITE]*F95608A9
DATASTREAM: Send MODE8 keepalive*F95608A9
[SERIAL WRITE]*F45608AE
[SERIAL DISCARD ECHO]

[steveo]

'echo corrupt' means the rx and tx lines aren't synchronized well or the buffer is gimpy. anything you transmit when rx and tx are tied together on a serial line should echo back an identical copy.

[Gojira94]

I'm not an EE, so this part might be more than I understand yet. My gut says maybe something with the ground on the ALDL side. What I did was use a good battery with charger on it (2A trickle setting). I used alligator clips to make connections in the following order: the PCM batt connection to the battery + / PCM ground to the battery - / PCM IGN to the battery +

To power the RS-232 I used a jump box with a lighter jack, plugged up to its own charger as insurance.

[steveo]

it could be, but keep this in mind; even with the cable unhooked from the aldl port, you still shouldn't get 'echo corrupt' messages while trying to connect. all that is required for a serial echo is loopback

[Gojira94]

Is there a loopback test I can do on the serial cable to see if it's the cable? Like short A & M together?

[Gojira94]

I ran across Dave W's posts about making a bench for LT1 vehicles and am trying his pinout ( http://www.gearhead-efi.com/Fuel-Injection/showthread.php?2807-Wiring-Schematic-for-bench-harness-LT1 ). I removed an extra BATT connection on black and moved the Data to blue 29. Will try it as soon as I get a moment to set up the bench again.

[Gojira94]

Tried it again with the updated pinout and got exactly the same result. Connetcs in TunerPro, fails in Winflash and $EEHack. Maybe it's time for a new, USB ALDL cable? I still have a hard time believing the serial cable would be bad. It came from AKM cables and works in every other way in/ on the car. Just having issues with it on the bench that I didn't have before.

[Gojira94]

It looks like I've been wrong about the A & M pins on the DLC end. Over at Shbox, I see this:

10853

Most of the diagrams I've been seeing everywhere else I've been reading upside down the orientation of A&M. Will try again...

[Gojira94]

Well, that wasn't it. I'm about out of ideas at this point. Same result, except with serial data to Blue 30, even TunerPro won't connect anymore. I don't want to throw money at it but I'd like to try a USB ALDL to see if that works.

[Gojira94]

So- one more to try. I saw this on another site. Looks to be meant for a 9C1 Caprice application, but I'll try it. Moving D30 back to D29 since I at least saw serial data in TunerPro before moving to 30.

10858

[Gojira94]

Still not working, same results. Is there something fundamentally wrong with trying to simply plug the ALDL interface to A&M into the harness? If the serial version of the ALDL cable didn't require a 12V power source I'd try pulling apart an old 9-pin serial cable or null modem cable and eliminating the ALDL cable entirely. So why does a serial ALDL cable need a power source to work?

[lionelhutz]

I have no idea why your serial port cable requires 12V. I have a serial adapter and it's powered from the serial port of the PC. The Express Card serial port adapter I was using wouldn't work with EEhack so I switched to a USB adapter.

I used an adapter from the Ebay link in post 4 of this thread.

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?4586-Building-16pin-ALDL-USB-cable-%2894-95-Camaro%29

I combined it with a 1N914 diode and a 1k resistor I already had. I also bought a cheap 10' USB extension cable so I could hard wire the adapter and use the USB cable to plug into my laptop. I simply plugged the adapter into my Windows 10 PC and it worked with the driver Windows found. The Red Devil River driver could also be tried if you have issues.

Some people say you can just connect the TX and RX together without the resistor and diode but I never tried it that way so I can't say if it would work that way or not.

[Gojira94]

It's a cable from either AKM or ALDLcable.com, bought it several years ago, exactly like this one:

http://www.aldlcable.com/products/aldlobd1.asp

I don't think it requires 12V, just needs a 12V connection, undoubtedly stepped down inside the serial connector end. To what, I don't know. I guess it's a rite of passage to build your own cable, but I'm getting further away from what I'm trying to do (yes, I'm whining). I'd feel comfortable working with one of these to do a USB cable (Thanks Mr. Isaar for the idea):

http://www.ebay.com/itm/FT232RL-USB-to-TTL-Serial-Converter-Adapter-Module-5V-and-3-3V-For-Arduino-F5-/301912485388?hash=item464b62ee0c:g:LWsAAOSw9uFW-f7h

But getting one of these from China or Hong Kong bothers me. I'd buy one in the US if I could find one (just started searching, may be out there somewhere). What I want (whining again) is a USB OBDI ALDL that works for logging and flashing, period or an answer on why the serial is giving me issues. I may bite the bullet and buy one from ALDL.com

[Gojira94]

Got a real USB cable from Red Devil River. Still had problems with it in the car in EEHack and WinFlash. Went back to the original design on my bench harness and it worked flawlessly. I flashed the PCM and a spare from a '94 Z28. Pulled the .bin after flashing and compared to what I assumed I was uploading and it was a match. I had modified the .bin slightly with TunerPro per my comments in post 9.


I still have code 84 setting after about 4-5 seconds. Watched it in Scan9495, reset, comes back in 4-5 seconds.


I tried looking at it in hex using the editor in TunerPro but don't know enough other than to look for addresses 00004dbe & 00004dc2. I don't see those addresses in any 95 auto bin I looked at from fbodytech. So it must be right. My sanity would be more stable if I'd seen those addresses with some sort of data next to them.

.bin file attached, if anyone can give me some assurance that 95 PWM code is present I would greatly appreciate it. I'm using the factory 16188051 PCM.

The ohm reading on all solenoids are within spec as read from the PCM harness connectors and PCM ign/ckt439. Maybe it's a fault in the trans wiring harness?

Thanks

[jthompson122183]

i have looked at the bin in post 30 and your good to go as far as using "95 pwm code". your problem lies elsewhere.

[Gojira94]

i have looked at the bin in post 30 and your good to go as far as using "95 pwm code". your problem lies elsewhere.Thanks for looking at it and apologies for the tardy reply. It's been... busy. With stuff I haven't wanted to deal with. Anyway, I'm thinking my next step will be to pull the harness out of the trans and see if anything unusual was done with it by the unknown builder. Bummer I don't have a known good 95 4L60E lying around, lol. I'll go out on a limb and speculate that maybe the builder put this thing together with something different electronically to sell it to buyers with 94 cars. If the trans was a bill of goods, what I've done should have worked, adding the wire from PCM to PWM solenoid and switching to 95 code.

[Gojira94]

I fished the case connector from the trans up to the engine bay. I'm going through the transmission wiring harness with it out of the car, connected up top so I can troubleshoot everything inside the trans as an assembly. It appears to be a reused OE harness because it only has one connector for the 3-2 solenoid. Aftermarket harnesses have 2 for the 3-2; one for 95 solenoid, one for 96-up solenoid connector.

Confirmed the valve body has a 95 casting mark on it so at long last that's confirmed.

All the tuning help I could have needed to address my problems with this thing I got here. Thanks again to all who reviewed my work. I thought I'd at least come back with the outcome. I'll post up the results of the electrical troubleshooting soon.

[Tom B.]

You may have a mechanical problem with the PWM valve and bore wear in the valve body. Another issue may be that the PWM (95-newer) transmissions use a different tcc spool valve in the pump. If your trans is a 94 w/a 95 valve body and no tcc valve swap, you can have all kinds of issues w/OD and lock up.

[Gojira94]

You may have a mechanical problem with the PWM valve and bore wear in the valve body. Another issue may be that the PWM (95-newer) transmissions use a different tcc spool valve in the pump. If your trans is a 94 w/a 95 valve body and no tcc valve swap, you can have all kinds of issues w/OD and lock up.

Thanks for offering additional insight! I should have mentioned that the case is a 95 K case and the pump does have PWM stamped on it and it was equipped with a 3-2 control solenoid appropriate for a 95. So on the surface everything seems to match as a 95 aftermarket built transmission. The transmission has about 1000 miles on it at most. I do see some friction material shed into the transmission from being driven with the 3-4 clutches getting extra wear as a result of it being driven by a 94 PCM and no control of the PWM solenoid (now corrected in the 95 tune and extra wire run to control the PWM control solenoid). I'm hoping that no mechanical problems due to wear in the valve body bores has arisen yet. I've accepted that if I get it operating error free, I'll have a transmission with some accelerated wear on it (like 20-30,000 miles of wear in less than 2,000 or something). Maybe higher simulated miles or worse damage than expected.

I'll be getting back to it later today and hopefully have some more answers.

[Gojira94]

Values in ohms are:

1-2 shift 21.2
2-3 shift 21.9
Press. Control 4.6
3-2 control 11.4
TCC 23.8
TCC control 11.2

Here's the bench- notice the PCM removed so I can apply voltage down the wire to pin E and ground through the PCM connector pins for each solenoid (except the pressure control solenoid). PCS can be tested with a 9V battery briefly. Testing from PCM down to solenoids gives me more confidence things are working. Honestly, I'm hoping to find something wrong with the harness and just replace it and be done.

[Gojira94]

I tested all the solenoids except the PCS, will have to dig up a 9V battery for that one, but I did check the resistance between the PCM pins that go to it (no direct 12V from pin E, only gets signal from PCM).

The 3-2 is the newest solenoid since I replaced it back in 2011 when I first encountered the issues. The PWM solenoid click doesn't sound nearly as stout as the 3-2. They are 2 different manufacturers, the PWM has been in there since before I got the car.

Here's the kicker- the TCC solenoid (built into the harness) does NOT click for me. I can't find a definitive answer as to whether it SHOULD make an audible click, but I'd at least think so. I tested 1-2, 2-3, 3-2, TCC, PWM with IGN239 circuit hot with PCM disconnected and used a small wire to ground the PCM connector pins at each solenoid's PCM location. To eliminate the engine harness I went through the case connector on pins E and T straight off the battery. Again, the TCC solenoid does NOT click. Its resistance is still at 24 ohms after this testing through PCM connectors and direct to battery.

[Gojira94]

I picked up a new harness with TCC solenoid. BWD S9844. Has Delphi printed on it in a couple places. Same manufacturer overseas makes a bunch of Delphi stuff these days, all the same. I tested the new harness the same way as the old one and this time I got a nice loud click from the TCC solenoid. Got the car all back together, just have to fill up the fluid and let it rip and scan for codes. It's too loud to fire up after 9PM in my neighborhood. Answers tomorrow. If it's fixed I'll learn to dance a jig, lol.

[Gojira94]

Tentatively going to say it's resolved. But not how it thought it would be.

Yes, the harness needed to be replaced due to the hidden issue with the TCC solenoid built into the harness. But that wasn't the cause of the code 84 3-2 downshift circuit problem that kept it in limp mode. I replaced the harness, buttoned it up, filled it up and crossed my fingers. I used GaryDoug's Scan9495 utility to monitor for trouble codes and the code 84 almost immediately popped back up. I'd clear it and it'd come right back in 2-3 seconds. Looking at the electrical faults tab in the program, it made me think from another direction when it said 'open circuit' on the 3-2 downshift solenoid circuit. I have a spare PCM...

The spare was from a 94 Z28 with 3.23s. So I threw it in and fired it up and scanned again. No codes, no circuit faults. The current PCM threw the code 84 under both 94 and 95 calibrations. I ran it for almost 20 minutes on the spare- no codes, no faults. Ok, so I can't use a 94 tune on a 95 trans. My 16210041 calibration ID on the PCM I've been using all along has the 95 code and some small mods for O2 relocation, etc., and has good data. Could the PCM internal circuit traces for the 3-2 circuit be damaged?

I set up my flash bench and uploaded the tune to the spare PCM with EEHACK 4.7 :thumbsup:. Threw it back in, crossed my fingers and... no codes. took it for a run around the block. Amazing to feel first gear in D at normal line pressure. I'll take it for a longer drive later and see how it goes. But it's never run for more than a few seconds before throwing the code 84 and now I've had 2 run cycles of nearly 25 minutes with no DTCs. I never considered the PCM might be at fault.

The mail order tune I got in 2010 was useless garbage and the reflash was good money after bad but it put me on the track of finding the hidden TCC solenoid problem and I learned more about the 4L60E. Way more than I wanted to actually, but it was good to learn.